The igniter is just a switch. It does the same job as a relay, but with no moving parts. It is there because the ignition coils require a relatively high current to operate (10 amps or so is common) and it is not efficient to carry that current over long distances, nor to switch it inside the ECU.

So, the igniter takes a low voltage, low current signal from the ECU (5 volts at a few milliamps) and uses it to switch the high-current power feeding the ignition coils.

The ignition coil itself is very similar to a transformer. A transformer can step an AC voltage up or down, by having two sets of windings; one heavy with a few turns, and the other thin with many turns. So if you have a transformer with a ratio of 1:10 and you put 100 volts at 1 amp into it, you will get 1,000 volts at 0.1 amps out of it. (In a transformer, current and voltage ramp inversely.)

The coil uses the same basic principle. There's a bunch of fanciness about magnetic flux collapse and whatnot, but essentially, you switch on the primary winding (with the igniter) and 12 volts at a high current starts to flow through the primary winding (the one with a few turns of thick wire). As it does this, it starts to generate a magnetic field in the core of the transformer (this takes several milliseconds, and is what we call the dwell time.) When the field has gotten strong enough, you switch the primary off, and that magnetic field collapses into the secondary winding (a bunch of turns of thin wire.) In doing so, starts to generate a very high voltage at a very low current. When the voltage gets high enough to jump the plug gap (this happens in microseconds), the plug fires.

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2 + 2 sometimes = 5

For unusually large values of two.

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Originally Posted by Braineack

^ I dont get it.

You see, the first guy asked "Have you ever farted in the TARDIS?" and the second guy said that yes, he had. It's utterly hilarious.

Just got home from work. ******* tourist....zomg. I am so ready for this to be over.

Good news though, I've made nearly 500 dollars in cash tips for the last two days and tonight I came home to a box with my name on it. In this box was my HDMI cable for my PS3 and a copy of Neon Genesis Evangelion 1.11 and 2.22 in Blu-Ray.

Just got home from work. ******* tourist....zomg. I am so ready for this to be over.

Good news though, I've made nearly 500 dollars in cash tips for the last two days and tonight I came home to a box with my name on it. In this box was my HDMI cable for my PS3 and a copy of Neon Genesis Evangelion 1.11 and 2.22 in Blu-Ray.

Can't wait for 3.33!!! I'm loving the remakes. It actually makes more sense now and sort of explains the details a bit better. And looks better.